Experimental investigation of the thermo-physical properties of water–ethylene glycol mixture based CNT nanofluids

The present study is aimed to measure and analyze the thermo-physical properties of water–ethylene glycol mixture based CNT nanofluids experimentally at various temperatures. The measured density data show observable deviation from the predictions of the Pak and Cho correlation, due to spontaneous filling of water inside the carbon nanotubes in a confined way. The presence of multi wall carbon nanotubes (MWCNT) enhances the specific heat of the nanofluids considerably, and this enhancement decreases with increase of the MWCNT concentration. The maximum thermal conductivity enhancement reaches up to 19.75% for the nanofluid containing 0.45 vol.% MWCNT at 40 °C. At a lower temperature range, the increase in the viscosity is low compared to the higher temperature for all the nanofluids. Further, the existing theoretical models could not predict the thermo-physical property values accurately, and the deviation has a great influence on the determination of the flow and heat transfer characteristics.

► The measured density data deviate from the well known mixing theory. ► The cp increases at 0.15 vol.% and the trend decreases with further MWCNT addition. ► Thermal conductivity increases due to ball milling, Brownian motion and liquid layering. ► Only a small increase in viscosity at 0–10 °C makes it suitable for cooling applications. ► The existing models could not well predict the property values of CNT nanofluids.